This invention provides synthetic polymer filaments having multilobal cross-sections. The filaments may be used in their as-spun form, for example, in yarns resulting from high speed spin-orientation or coupled spin-drawing processes, or may be used as feed yarns for de-coupled drawing or draw texturing processes. The multifilament yarns made from these filaments are useful to make articles with subdued luster and low glitter.
There is a desire to provide textured multifilament yarns capable of being converted into knitted or woven fabrics having no undesired glitter. Draw false twist texturing is a method for producing textured multifilament yarns by simultaneously drawing and false-twist texturing undrawn multifilaments. Draw false twist texturing of filaments eliminates the undesirable slickness of fabrics made from synthetic filaments as well as provides filaments with bulk, which provides better cover. However, false twist texturing and draw false twist texturing of filaments having round cross-sections deform the cross-sections of the filaments to a multi-faceted shape having essentially flat sides. As a result, fabrics made from these textured filaments exhibit a specular reflection from the flattened fiber surfaces creating an undesired glittering or sparkle. In addition, the denier per filament (dpf) may be reduced, for example, to improve the softness of the yarns, fabrics and articles produced therefrom, to less than about 5 dpf, or even to deniers below about 1. Such subdenier filaments are also known as xe2x80x9cmicrofibersxe2x80x9d. At these subdeniers, the total amount of this specular reflection is dramatically increased, due to the increase in total fiber surface area.
Efforts to eliminate the glitter and sparkle associated with filaments having a round cross-section has led to the development of various multilobal cross-sections. For example, U.S. Pat. Nos. 5,108,838, 5,176,926, and 5,208,106 describe hollow trilobal and tetralobal cross-sections to increase the cover to minimize the weight of fiber needed to spread over an area. These patents relate specifically to carpet yarns and higher denier filaments, and not to filaments suited for apparel or twist texturing.
Other modified cross-sections have also been attempted to reduce the glitter from round cross-sectional filaments. For example, U.S. Pat. No. 4,041,689 relates to filaments having a multilobal cross-section. Moreover, U.S. Pat. No. 3,691,749 describes yarns made from multilobal filaments prepared from PACM polyamide. However, the filaments described in these patents still need to be textured prior to use and do not provide a means to reduce glitter of fine denier and especially subdenier filaments, yarns, fabrics and articles produced therefrom.
Other efforts to reduce glitter include the use of polymer additives. For example, delustrants, such as titanium dioxide, have been used to decrease the glittering effect from textured yarns. However, such delustrants alone have been ineffective in reducing the glitter of fibers having fine deniers.
Various fiber and fabric treatments have been proposed that effect glitter including caustic treatments. However, such caustic approaches have inherent disadvantages such as added costs and/or increased waste by-products.
The use of multicomponent fibers to reduce the glitter effect has also been attempted. For example, U.S. Pat. No. 3,994,122 describes a mixed yarn comprising 40-60% by weight of trilobal filaments having a modification ratio within the range of 1.6-1.9, and 40-60% by weight of trilobal filaments having a modification ratio within the range of 2.2-2.5. In addition, U.S. Pat. No. 5,948,528 describes obtaining a filament having modified cross-sections for bicomponent fibers, wherein the fibers are composed of at least two polymer components having different relative viscosities. While yarns made from such multicomponent filaments have a bulking effect that does not necessarily require additional texturing, the production of these fibers are encumbered by the necessity to use a mixture of two or more different polymers or fibers.
Accordingly, there is a need to obtain a filament that can be used to make yarns, and articles therefrom, such as fabrics and apparel, having reduced glitter and shine without the necessity for high levels of added delustrants or fabric after-treatments, and that provide the desirable low glitter and shine without the need for additional texturing. Additionally, there is a need, that, if desired, the filaments can be textured, including by false-twist texturing or by draw false-twist texturing, and still provide the desirable low glitter and low shine to the yarns, fabrics and articles produced therefrom. There is additionally a need to obtain a low denier filament, preferably a filament that can be drawn to a subdenier filament, and especially preferred a filament that is subdenier as-produced, that provides low glitter and shine to the fine denier yarns, fabrics and articles produced therefrom. These low denier and subdenier filaments should have sufficient tensile properties to enable the filaments to be subsequently processed, with low levels of broken filaments, into fabrics and articles therefrom.
In accordance with these needs, the present invention provide a synthetic filament having a multilobal cross-section, a filament factor of about 2 or greater, wherein the filament factor is determined according to the following formula:
FF=K1*(MR)A*(N)B*(1/(DPF)C[K2*(N)D*(MR)E*1/(LAF)+K3*(AF)], 
wherein K1 is 0.0013158; K2 is 2.1; K3 is 0.45; A is 1.5; B is 2.7; C is 0.35; D is 1.4; E is 1.3; MR is R/r1, wherein R is the radius of a circle centered in the middle of the cross-section and circumscribed about the tips of the lobes, and r1 is the radius of circle centered in the middle of the cross-section and inscribed within the cross-section about the connecting points of the lobes; N is the number of lobes in the cross-section; DPF is the denier per filament; LAF is (TR)*(DPF)*(MR)2, wherein TR is r2/R, wherein r2 is the average radius of a circle inscribed about the lobes, and R is as set forth above, and DPF and MR are as set forth above; and AF is 15 minus the lobe angle, wherein the lobe angle is the average angle of two tangent lines laid at the point of inflection of curvature on each side of the lobes of the filament cross-section, and an average tip ratio of xe2x89xa7 about 0.2.
In another embodiment of the invention, a filament having a multilobal cross-section, wherein the lobe angle is xe2x89xa6 about 15xc2x0 and a denier of less than about 5 dpf is disclosed.
The present invention is further directed to multifilament yarns formed at least in part from the filaments of the present invention, and fabrics and articles formed from such yarns.
In another aspect of the invention, a spinneret capillary correlating to a multilobal cross-section with a filament factor of about 2.0 or greater and a tip ratio of greater than about 0.2 is disclosed.
In yet another aspect of the invention, there is provided a process for making a filament having a multilobal cross-section, wherein the filament cross-section has a filament factor of xe2x89xa7 about 2.0 and a tip ratio of xe2x89xa7 about 0.2, said process comprising melting a melt-spinnable polymer to form a molten polymer; extruding the molten polymer through a spinneret capillary designed to provide a cross-section having a filament factor of xe2x89xa7 about 2.0 and a tip ratio xe2x89xa7 of 0.2; quenching the filaments leaving the capillary; converging the quenched filaments; and winding the filaments.
The present invention is further directed to a method for reducing glitter in fabric comprising forming said fabric using at least one filament having a multilobal cross-section, a filament factor of about 2 or greater, and a tip ratio of xe2x89xa7 about 0.2.